Dynamic response of closely-attached intersecting underground subway structures under vertical strong ground motion

It is important for subway approaching excavation and safe management to study the seismic response characteristics of closely-attached intersecting underground subway structures. The finite difference procedure FLAC^3D is used to simulate the seismic response of typical closely-attached intersecting underground subway structures under vertical strong ground motion in Beijing, of which the seismic response characteristics are analyzed carefully and compared with those of a single subway station as well. It is shown that there are significant changes in the vertical displacement and the stress of structures between the single subway station and the closely-attached intersecting subway station because of the strong interaction of the upper station and the lower tunnel, which is also in connection with input ground motion, and that the monitoring parts have the same variation amplitudes. As soils can filter high frequency component of ground motion significantly, the vertical displacement difference and the vertical stress difference between the above two kinds of subway stations under vertical strong ground motion rich in high-frequency waves are smaller than those rich in low-frequency waves, while they are not sensitive to peak acceleration of input ground motion.